1) Field of the Invention
The invention relates to an air outlet valve for use in an aircraft which is adapted during normal operation of the aircraft as a component of a cabin pressure control system for adjusting a desired pressure level in an aircraft cabin to remove air from an interior of the aircraft into the environment around the aircraft, and which is further adapted during emergency ventilation operation of the aircraft, when the aircraft cabin can no longer be supplied with sufficient breathable air by an aircraft air-conditioning system, as a component of a system for emergency ventilation of the aircraft cabin to introduce air from the environment around the aircraft into the interior of the aircraft.
2) Discussion of the Prior Art
At present, in passenger aircraft a so-called air-assisted air-conditioning system is conventionally used to air-condition the aircraft cabin. The aircraft air-conditioning system is used to cool the aircraft cabin, which would otherwise become too warm as a result of thermal loads, such as for example solar irradiation, body heat of the passengers and waste heat from equipment on board the aircraft. The air-conditioning system moreover supplies enough fresh air into the aircraft cabin to ensure that there is a specified minimum oxygen content in the aircraft cabin. Finally, the air-conditioning system is used to keep the pressure in the aircraft cabin at a level higher than the atmospheric pressure when the aircraft is flying above a specific altitude. The cabin internal pressure is controlled by means of a cabin pressure control system, which comprises controllable air outlet valves disposed in the fuselage of the aircraft.
The air outlet valves of the cabin pressure control system are disposed in the region of a skin of the aircraft fuselage and conventionally comprise one or two flaps that are pivotable about an axis. The pivot axis or axes of the flap(s) may be positioned centrally or laterally relative to the flap(s). For controlling the cabin internal pressure, the air outlet valves are controlled in dependence upon the pressure prevailing in the aircraft cabin and upon the operating state of the aircraft. During cruising of the aircraft the air outlet valves are usually almost closed. In contrast thereto, the air outlet valves are as a rule fully open when the aircraft is situated on the ground, i.e. the setting angle of the flap(s) is ca. 90° in order to guarantee complete depressurization of the aircraft cabin.
If during flight a defect in the aircraft air-conditioning system arises that has the effect that the aircraft cabin can no longer be supplied with sufficient fresh air, the aircraft descends to a safe altitude, at which it is no longer necessary to keep the pressure in the aircraft cabin at a level higher than the atmospheric pressure, and flies unpressurized to the destination airport or to an airfield situated closer by. In order to supply the necessary breathable air for the passengers during this period, it is known for example from the non-pre-published DE 10 2008 058 451 to provide aircraft with one or more emergency ram-air inlets, through which ram air from the environment around the aircraft may be directed into the interior of the aircraft.
From the likewise non-pre-published DE 10 2008 056 417 a system for emergency ventilation of an aircraft cabin is further known, which comprises a first valve disposed in a first aircraft fuselage region as well as a second valve disposed in a second aircraft fuselage region spaced apart along a longitudinal axis of the aircraft from the first aircraft fuselage region. The first and the second valve are used during normal operation of the aircraft as air outlet valves of an aircraft cabin pressure control system. During emergency ventilation operation the first and the second valve may however be controlled by an electronic control unit in such a way that a negative-pressure-driven emergency ventilation of the aircraft cabin arises, in which air from the environment around the aircraft is supplied through the open first valve into the first aircraft fuselage region and directed from the first aircraft fuselage region into the aircraft cabin. After flowing through the aircraft cabin the air is directed into the second aircraft fuselage region and finally removed through the open second valve into the environment around the aircraft.
Known air outlet valves for use in a cabin pressure control system have the drawback that, because of their construction, they are completely incapable or capable only to a limited extent of directing air from the environment around the aircraft into the interior of the aircraft. For example, a conventional air outlet valve having flaps that are pivotable about pivot axes disposed laterally relative to the flaps cannot be used in a system for emergency ventilation of an aircraft cabin to direct air from the environment around the aircraft into the aircraft cabin. Rather, an—in relation to the flying direction of the aircraft—front or nose-side flap of the air outlet valve, as shown in FIG. 1, prevents air from being able to pass from the environment around the aircraft into the interior of the aircraft. A valve configured in this way is therefore usable exclusively as an air outlet valve.
Admittedly, in the case of an air outlet valve having flaps that are pivotable about pivot axes disposed centrally relative to the flaps, a ram pressure arising at an—in relation to the flying direction of the aircraft—front or nose-side flap of the air outlet valve, as depicted in FIG. 2, ensures that air may be directed from the environment around the aircraft into the interior of the aircraft. However, in a region of the air outlet valve situated between the pivot axis of the nose-side flap and the pivot axis of an—in relation to the flying direction of the aircraft—rear or tail-side flap, pressure conditions arise which have the effect that air passes from the interior of the aircraft into the environment around the aircraft. This applies also to a region of the air outlet valve situated—in relation to the flying direction of the aircraft—behind the pivot axis of the tail-side flap. Such an air outlet valve is therefore also suitable only to a limited extent for use in a system for emergency ventilation of an aircraft cabin.